No where in settings or on the phone does it say HD voice. I do VOIP installs and can tell you, this phone is no polycom with HD voice. That said, it sounds better than my evo when on the phone. But remember you are taking that from a guy with hearing loss and tone deafness.
Sorry, I don't need to root the phone so I have not tried any roots on it.
I activated it on Sprint. My EVO had 6 months to go before the contract was up. I am hard on phones so for less than the deductible on insurance I bought this phone. If you look at it as a phone that costs less than 1/4 (or so) of a galaxy S5 it's a nice phone. If you compare it to an S5, your gonna hate it. I have it on the framily plan with sprint.